Interlocking system for railroads



March 15, 1938'.

' J. l. VAUGHN INTERLOCKING SYSTEM FOR RAILROADS Filed May 28, 1957 2Sheets-Sheet l n v ii m? $02 m m mm I u n Qzn %3 u H H W n INVENTOR I BY2 A TORNEY March 15, 1938. J. a. VAUGHN INTERLOCKING SYSTEM FORRAILROADS Filed May 28, 1937 2 Sheets-Sheet 2 A4. ORNEY Patented Mar.15, 1938 UNITED STATES PATENT OFFlCE John I. Vaughn, Rochester, N. Y.,assignor to General Railway Signal Company, Rochester,

Application May 28, 1937, Serial No. 145,338

13 Claims.

This invention relates to interlocking systems for railroads, and moreparticularly to interlocking systems automatically operated by thepresence of trains.

This invention provides for the automatic setting up of routes throughan interlocking plant by the presence of trains on the approach tracksections to such routes. There is also provision made whereby alternatemoves will be made over two conflicting routes when three or more trainsarrive concurrently on the two routes.

The present invention also contemplates certain safety featuresparticularly adaptable to railway practice. For example, it is wellknown to those familiar with the art of.railway signalling that taking aclear signal away from. an approaching train and permitting aconflicting route to be immediately set up is a dangerous condition, andshould be prevented by giving the approaching train sufficient time tohave either come to a stop or proceeded far enough into a route to haveprevented the setting up of a conflicting route by having dropped thetrack relay of the detector track section.

Although the present system does not provide means under normalautomatic operation whereby a signal can be taken away from anapproaching train, there are certain accidental conditions which mightcause such operation, such as momentary opening of a circuit due to abreak in a wire, high resistance developing in a contact, or improperoperation of a relay. Other conditions which might cause a signal to goto danger in front of an approaching train are the momentary loss ofshunt under the approaching train, mo-

mentary dropping of a detector track relay, dropping of a leaving trackrelay by a train entering the interlocking from the opposite direction.

This invention provides a system wherein the above conditions do notallow improper or unsafe operations to occur by reason of the use of atime element, which time element also provides for the emergency releaseof routes requiring similar safety protection.

Other objects, purposes and characteristic features of the presentinvention will in part be pointed out hereinafter and will in part beapparent from the accompanying drawings. Any invention common to thisapplication and the application of Wight Ser. No. 145,337 filed on thesame date as the instant application will be claimed in said Wightapplication, and no claims to said common invention will be made herein.

The accompanying drawings (Figs. 1A and 1B) show one embodiment of thepresent invention as applied to a railway crossing system in which eachtrack is signalled for both directions.

With reference to the drawings, the railway track A is illustrated asdivided into track circuits 4, 5 and 6 and crossed by railway track Bwhich is divided into track circuits '1, 8 and 9. This trackway has beenindicated symbolically by single lines to conserve in space for theremaining parts of the invention.

The signalling arrangement comprises a means of governing trafiicthrough the interlocking in either direction on each track. The signalsillustrated are of the search light signal type, as shown in the PatentNo. 1,835,150, granted to O. S. Field December 8, 1931, which areprovided with contacts that are closed when the signal indicates dangerand open when the signal indicates clear. Signals IE! and H governtraffic over track A, signal In governing east bound traffic and signalll west-bound traffic. Signals l2 and i3 govern trafiic over track B,signal 12 governing east-bound trafiic and signal l3 west-bound traffic.

Although search light signals have been illustrated, it is to beunderstood that color light signals having individual lamp units couldas well be used, the green lamp being illuminated through a circuitincluding a front contact of a signal control relay, and the red lampbeing illuminated through a circuit including a back contact of saidsignal control relay. A back contact on said signal control relay couldbe used in place of the contact illustrated as part of the mechanism ofthe search light signal.

The relays l0--ll and l2-l3 are of the polarneutral type and are used insetting up the route required under the various trafiic conditions.

The relay MS is a slow release relay associated with the route controlrelays and is used in establishing a time interval between the placingof a signal at danger in front of an approaching train and the clearingof a signal governing traffic over a conflicting route.

The relays AS and BS are associated with the approach track sections andare conveniently termed receding stick relays as they prevent a recedingroute from being set up by a train leaving the interlocking when theapproach track relay for that route is dropped.

The relays AGR. and BGR are used in checking the danger position of thevanes in the signal mechanisms.

Relays AMR and BMR are slow release relays associated with the operationof the emergency release push-button.

The thermal relay TM is associated with the control of relay MS andprovides the time interval required under the conditions hereinafterdescribed.

The emergency release button PB is located so as to be conveniently usedby the train men of either track and has also associated with it anindicator lamp E and switch SW to indicate when all the signals are atdanger.

For the purpose of simplifying the illustration and facilitating in theexplanation, various parts and circuits constituting the embodiment ofthe invention have been shown diagrammatically, the drawings have beenmade more with the purpose of making it easy to understand theprinciples and mode of operation than with the idea of i1- lustratingthe specific construction and arrangement of parts that would beemployed in practice. The symbols and are employed to indicate thepositive and negative terminalsrespectively of suitable batteries, orother sources of direct current; and the circuits with which thesesignals are used always have current flowing in the same direction.

The track relays are all energized under normal conditions through theirrespective track circuits, the detail of said circuits not being shownas these are well known to those familiar with the art.

As the signals are normally at danger, the relays AGR and BGR arenormally energized through contacts closed when the signals are in theirdanger position.

Relay AGR is energized from through a circuit including contact ofsignal ll, contact 2| of signal In, winding of relay AGR, to

In a similar manner relay BGR is energized from through a circuitincluding contact 22 of signal l2 and contact 23 of signal l3, windingof relay BGR, to

When these relays are energized, the stick circuit for relay MS iscompleted, the energization of which was effected by the last trainpassing through the interlocking plant. Relay MS is held in itsenergized position from through a circuit including front contact 24 ofrelay BGR, front contact 25 of relay AGR, winding of relay TM, frontcontact 26 of relay 8T, front contact 21 of relay 5T, front contact 28of relay MS, winding of relay MS, to Although this circuit includes thewinding of thermal relay TM, it is evident that the high resistance ofthe winding of relay MS is sufficient to limit the flow of current inthe winding of relay TM so as to cause its contacts to remain in theirnormal position.

With no trains within the limits of the interlocking plant and therelays in their normal position, assume a train approaching on track Ato have entered track section 4, thus setting up a route through theinterlocking plant in a manner about to be described in detail.

The dropping of relay 4T causes the energization of relay !0ll fromthrough a circuit including front contact 29 of relay 6T, back contact30 of relay 4T, front contact 3| of relay 5T, back contact 32 of relayAS, back contact 33 of relay BMR, back contact 34 of relay l2-l3, frontcontact 35 of relay MS, winding of relay |0l I, back contact 36 of relay4T, front contact 31 of relay BT, to When relay lO-Il picks up it closesa stick circuit through its front contacts 13 shunting front contact 35of relay MS out of its control circuit.

With the route relay l0-ll in its energized position and the detectortrack circuits unoccupied, a circuit is closed for energizing thecontrol mechanism in signal 3 to its clear position from through acircuit including front contact 38 of relay 8T, front contact 39 ofrelay 5T, back contact 40 of relay TM, front contact 4| of relay ill-4|,back contact 42 of relay l2-l3, front contact 43 of relay BGR, polarcontact 44 of relay lEJ-H in its right hand position, winding of signalIt] mechanism relay, to The energization of the Winding of the signalmechanism effects the operation of the vane of the mechanism in such away as to substitute the green spectacle for the red spectacle in linewith the beam of light emitted from the signal.

It may be well to point out at this time that the route relays l0ll andl2-l3 are electrically interlocked so that only one may be energized ata time, and also that the signals for one track may be cleared only whenthe route relay for the other track is down.

The opening of contact 2i of signal i0 when signal l0 clears deenergizesrelay AGR, and the opening of front contact 25 of relay AGR effects thedropping of relay MS.

As a train accepts signal l0 and drops track relay 5T the control ofsignal Ii] will be deenergized by reason of front contact 39 of relay 5Tbeing opened. The Winding of the signal control mechanism beingdeenergized effects the replacement of the green spectacle with a redspectacle in line with the beam of light emitted from the signal.

The dropping of the detector track relay 5T closes a circuit forenergizing the relay AS from through a circuit including front contact38 of relay 8T, back contact 39 of relay 5T, winding of relay AS, to

As the train enters track circuit 6 and drops relay 6T a circuit isclosed for energizing relay MS from through a circui including frontcontact 45 of relay BGR, front contact 46 of relay AGR, back contact 41of relay 5T, polar contact 48 of relay Ill-4| in its right handposition, back contact 49 of relay 6T, winding of relay MS, to

The dropping of relay 6T closes the stick circuit for relay AS fromthrough a circuit including back contact 56 of relay 6T, front contact5! of relay 4T, front contact 52 of relay AS, Winding of relay AS, to

As the train leaves track section 5 and relay 5T picks up, the circuitfor energizing relay MS is broken through back contact 41 of relay 5T;relay MS, however, being a slow release relay will remain in its pickedup position until its stick circuit is completed by the closing of frontcontact 21 of relay 5T.

The relay AS having been picked up when the train entered the detectortrack section and held in its energized position until the train hasleft track section 6, locks out the control of relay Iii-ll by openingthe circuit at back contact 32, thus preventing the setting up of aroute when the relay 6T drops, due to the passage of the train throughtrack section 6 while leaving the plant.

As the train leaves the interlocking plant, relay AS is deenergizedthrough the opening of the circuit at back contact of relay 6T.

Having thus described the operation during the passage of a train overtrack A, assume a train to approach signal l2 on track B under similarconditions, the interlocking plant being unoccupied when the trainapproaches.

The dropping of relay 1T closes a circuit for energizing relay I2--I3from through a circuit including back contact 53 of relay 1T, frontcontact 54 of relay 9T, winding of relay l2-i3, front contact 55 ofrelay MS, back contact 56 of relay Iii-4 I, back contact 51 of relayAMR, back contact 58 of relay BS, front contact 59 of relay 8T, frontcontact 60 of relay 91, back contact El of relay IT, to As soon as relayI2-l3 picks up it shunts front contact 55 of relay MS out of its controlby a circuit through its own front contact 62.

When relay i2-l3 is in its energized position a circuit is closed forenergizing the control winding in signal I2 from through a circuitincluding front contact 38 of relay 8T, front contact 39 of relay 5T,back contact as of relay TM, front contact 42 of relay l2-l3, backcontact M of relay lllll, front contact 655 of relay AGR, polar contact64 of relay l2l3 in its right hand position, winding of the controlmechanism in signal if, to The energization of said winding causes thevane in the signal to rotate to a position where the beam of light willpass through the green spectacle instead of the red spectacle.

Relay BGR is deenergizedby the opening of contact 22 on signal 12 whensignal It is cleared, the dropping of which relay opens the controlcircuit of relay MS at front contact 24.

As the train accepts signal [2, the control of the signal is opened atfront contact 38 of relay BT, thus causing the green spectacle which wasin line with the beam of light emitted from the signal to be replacedwith a red spectacle.

The dropping of relay 8T also closes a circuit for energizing relay BSfrom through a circuit including back contact 38 of relay 8T, winding ofrelay BS, to

As the train enters track section 9, the dropping of track relay 9Tcloses a circuit for energizing relay MS from through a circuitincluding front contact 45 of relay BGR', front contact 46 of relay AGR,back contact 65 of relay 8T, polar contact 86 of relay I2-I3 in itsright hand position, back contact 6i of relay 9T, winding of relay MS,to

The dropping of relay 9T also closes the stick circuit for relay BS fromthrough a circuit including front contact 68 of relay 1T, back contact69 of relay 9T, front contact 10 of relay BS, winding of relay BS, to

It will be noted that the opening of back contact 53, when relay BSpicks up, opens the control of relay I2I3, thus preventing theenergization of relay |2l3 on reverse polarity and the clearing ofsignal [3 after the train leaves the detector track circuit.

As the train leaves track section 8, the control of relay MS is openedby the picking up of relay 3T, but the relay remains in a picked upposition due to its slow release feature until the closing of frontcontact 26 of relay 8T completes its stick circuit.

As the train leaves the interlocking plant, the opening of back contact69 of relay 9T when relay 9T picks up, deenergizes relay BS, and thesystem is again restored to its normal conditions.

Having thus described in detail the passage of a train through theinterlocking plant from west to east on each of tracks A and B, it isobvious that the operation for the passage of trains from east to Westis similar to that just described and employs the same control circuitsfor the route relays, using opposite polarity, the signal controls andenergization controls for relay MS being selected by the polar contactsin the left hand position.

The use of the thermal relay TM provides a time interval between thetime when a signal changes from clear to danger and the clearing of anysignal, providing that the detector track sections are unoccupied theoperation of this relay can best be understood by assuming a trafficcondition under which the operation of the relay is required.

Assume a train to approach signal ill on track A, clearing the signal ina manner similar to that previously described, and a few moments later atrain to approach signal 12 on track B and entering the approach sectionlT, thus receiving a danger indication from signal I? on account ofsignal [0 being clear.

If, for some reason, the route relay i9ll is deenergized, thus causingsignal Hi to go to danger, neither route relay may be energized untilrelay MS is first picked up through a back contact on the thermal relayTM. Both of the signals ill and I? will display a danger indicationuntil one of the route relays is energized.

The energizing circuit for relay TM is from through a circuit includingfront contact 2 of relay BGR, front contact 25 of relay AGR, winding ofrelay TM, front contact 26 of relay ST, front contact 27 of relay 5T,back contact 28 of relay MS, to

The closing of the front contact on relay TM at the end of the timeinterval closes a circuit for energizing relay MS from through a circuitincluding front contact 24 of relay BGR, front contact 25 of relay AGR,front contact M of relay TM, winding of relay MS, to The relay MS in itspicked up position closes its stick circuit as has previously beendescribed.

There having been sufficient time for an approach train on track A tohave come to a stop before passing signal l0, either of the two routerelays may now be energized with relay MS in its energized position,depending upon which one has the quicker operating characteristics. Ifthe approaching train on track A had not been able to stop in the rearof signal ill and had dropped track relay 5T, it would have opened thecontrol circuit for relay IU-ii at front contact 35 of relay BT, andalso opened the signal control circuit at front contact 39 of relay ET.This condition ,would allow route relay i"-i3 to pick up but would notallow signal I2 to clear due to the control of that signal being open.

Again assume two trains to have been approaching on tracks A and Brespectively, the first train having cleared signal it. An emergencyrelease of the route set up so as to clear signal l2 for the train ontrack B may be accomplished by the operation of the emergency releasepush button located so as to be accessible to the trainmen from eithertrack.

Assume a trainman to press the button PB under said conditions. Acircuit is closed for energizing relay BMR from through a circuitincluding front contact 2 5 of relay BGR, back contact 25 of relay AGR,contact at of push button PB, winding of relay BMR, to

Relay MS, having been deenergized upon the clearing of signal l5 closesa stick circuit for relay BMR from through a circuit including backcontact 1! of relay MS, front contact 12 of relay BMR, winding of relayBMR, to

The picking up of relay BMR opens a circuit for the control of relayHl|l at back contact 33, thus causing signal l to go to danger, whichwill cause the energization of relay TM through a circuit as previouslydescribed. The closing of back contact "i l of relay TM causes theenergization of relay MS which in turn closes the control of relay|2--l3 through its front contact 55, and signal I2 is cleared as aresult of the picking up of the relay l2|3.

The picking up of relay MS opens the stick circuit for relay BMR at backcontact H. Relay BMR is slow in releasing thus allowing relay l2--l3time to pick up, in preference to relay lG--l l, by locking out thecontrol of relay ll l at back contact 33. This obviously insures thepicking up of the relay for the route to be cleared in preference to therelay for the route just released.

An indicator lamp is associated with the emergency release push buttonto indicate when the signal for the route to be released has gone todanger and also when the signal for the route desired has been cleared.A switch SW has been shown in series with the indicator lamp E. whichswitch is closed when the door of the push button housing is open, so asto allow the indicator light E to be illuminated only at such times asthe operation of the emergency release is desired. The indicator lamp Eis illuminated when the signals are all at danger through a circuit from(-1-), including front contact H of relay MS through the switch SW inits closed position, indicator lamp E, to

When signal [2 clears and relay MS drops, the control of the lamp E isopened at front contact ll thus indicating to the trainman that signall2 has been cleared.

Alternate moves over two conflicting routes are provided under heavytrafiic conditions by allowing a route relay on one route to be pickedup while there is a train passing through an interlocking plant on aconflicting route, and the presence of said train on the detector tracksection holds that conflicting route relay down. The signal governingtraffic over the route for which the route relay was energized will notclear until the detector track sections for both tracks are unoccupied.

This feature of the invention can best be understood by assuming an eastbound train M on track A to be passing through the plant, and at thesame time approach sections G and I of tracks A and B respectively tobecome occupied by approaching trains N and 0, respectively. The routerelay l2-l3 picks up as soon as the train 0 approaching on track Benters section 1, regardless of the fact that the approaching train N ontrack A may have entered section 4 prior to the train 0 on track Bhaving entered section I. The circuit for the control of relay l2-l3 isclosed, with the train 0 on approach section 'I, as soon as relay l0-Hdrops and closes back contact 56 provided the relay MS has beenreenergized, it having been dropped by passing of train M over tracksection 5.

After the first train M on track A leaves the interlocking plant, signall2 clears; and, after the train 0 on track B has accepted signal l2 andthe route relay l2l3 has been dropped by reason of the opening of thecircuit at front contact 59 of relay 8T, a circuit is closed forenergizing relay Ill-ll at back contact 34 of relay l2-I3, assuming thatrelay MS has been picked up since the train accepted signal l2. Withrelay IDII picked up, signal l0 clears for the train N on track A assoon as the train 0 on track B leaves track section 8 and track relay 8Tcloses its front contact 38.

In a similar manner alternate moves are provided for as many trains asmay occupy two approach sections, such as, 4 and i, 4 and 9, 6 and 1 or6 and 9, before a train passing through the interlocking has passedentirely off the detector and approach sections of tracks A and Brespectively.

It is obvious, from the example given, that the selection of a frontcontact of the track relay for the detector track section and theselection of a front and a back contact of the two approach track relaysrespectively, in the control of the route relay for that route, is themeans for providing said alternate operation. It is also obvious thatsimilar operation is provided for train movements from east to West.

Having thus shown one particular embodiment of the present invention asapplied to a track layout having a railway crossing, it is desired to beunderstood that the invention is not limited to the particular type ofsystem as shown in the drawings, and that additions, modifications andchanges may be made to adapt the invention to the particular signalproblem encountered in practice, all without departing from the spiritof the present invention or its scope, except as de manded by the scopeof the following claims.

What I claim ist- 1. In a tramc controlling system for railroads; atrack layout having a plurality of conflicting routes; signals forgoverning traffic over said routes; a neutral relay; means for at timesclearing one of said signals only if said neutral relay is picked up; athermal relay; a detector track section for each route; a circuit meansfor picking up said neutral relay when said signals are all at stop, andsaid thermal relay has completed its operation to its energized positin; circuit means for energizing said thermal relay when said neutralrelay is dropped away providing said detector track sections areunoccupied and said signals are at stop; circuit means for picking upsaid neutral relay independently of the operation of said thermal relay,when a train is leaving a detector track section; and circuit means forretaining said neutral relay in its picked up position when saiddetector track sections are unoccupied and said signals are at stop.

2. In a traflic controlling system for railroads; a track layout havingat least two conflicting routes; signals for governing trafilc over eachroute; an approach track section for each signal; a route relay for eachroute; circuit means for energizing each one of said route relays whenits approach section is occupied, but effective to energize only one ofsaid route relays at any one time; a time element device; a manuallyoperable contactor; circuit means responsive to the operation of saidcontactor for effecting the release of one of said route relays,followed by the energization of a second route relay for a conflictingroute, only at the end of a predetermined time interval measured by saiddevice; and circuit means for clearing each signal when and only whenthe route relay for such signal is energized.

3. In a traflic controlling system for railroads; a track layout havinga plurality of conflicting routes; signals for governing traffic overeach route; an approach section for each signal; a route relay for eachroute; circuit means for energizing each of said route relays when atrain occupies an approach section for that route; circuit means forallowing the energization of the route relay for only one conflictingroute at any one time; a time element device; a manually operablecontactor; circuit means for allowing the energization of a second routerelay, only after said device has completed its operation, providing theenergization of said device has been rendered effective by the releaseof a first route relay due either to the manual operation of saidcontactor or to an abnormal operating condition; and circuit means forclearing each signal only when the route relay for that signal isenergized.

4. In a traffic controlling system for railroads; a track layout havinga first stretch of track crossed by a second stretch of track; signalsfor governing traffic over each track; an approach section for eachsignal; a route relay for each track; circuit means for energizing eachof said route relays when a train occupies an approach section for thatroute; circuit means for allowing the energization of only one routerelay at any one time; circuit means for energizing alternately firstone route relay and then the other route relay as long as followingtrains occupy approach sections on both tracks before a preceding trainhas left the approach section for the opposing signal on that particulartrack; and circuit means for clearing each signal only when itsrespective route relay is energized.

5. In a trafiic controlling system for railroads; a first stretch oftrack crossed by a second stretch of track; signals for governingtrafiic over each track; an approach section for each signal; a routerelay for each track; circuit means for distinctively energizing each ofsaid route relays when a train occupies its respective approach section;said circuit means including means for allowing the energization of onlyone route relay at any one time; a time element device; a manuallyoperable contactor for releasing a first route relay and rendering saiddevice effective; circuit means for energizing a second route relay onlyafter said device has completed its operation, providing said device hasbeen rendered operable by the operation of said contactor; circuit meansfor energizing alternately first one route relay and then the otherroute relay when following trains occupy approach sections or bothtracks before a preceding train has left the approach section for theopposing signal on that particular track; and circuit means for clearingeach signal when its respective route relay is energized in a particulardistinctive position.

6. In a traffic controlling system for railroads; a track layout havinga first stretch of track crossed by a second stretch of track; signalsfor governing trafiic over each stretch of track; an approach sectionfor each signal; a route relay for each track; circuit means forenergizing each of said route relays when an approach section for thattrack is occupied; said circuit means including means for allowing theenergization of only one route relay at any one time; circuit means forcausing said route relays to be energized alternately, when and onlywhen trains occupy approach sections on both tracks before a precedingtrain has left the approach section for the opposing signal on thatparticular track; a time element device; circuit means for renderingsaid device operable when by reason of an abnormal operating condition afirst route relay is deenergized; circuit means for permitting theenergizaticn of a second route relay only after said device hascompleted its operation, providing said device has been renderedoperable; and circuit means for permitting the clearing of only onesignal when the route relay for that track is energized.

'7. In a trafiic controlling system for railroads; a track layout havingat least two conflicting tracks; signals for governing traflic over eachof said tracks in both directions; an approach section for each signal;a route relay for each track; circuit means for energizing each of saidroute relays when one of its respective approach sections is occupied;said circuit means including means for allowing the energization of onlyone of said route relays at any one time; circuit means for causing saidtwo route relays to be alternately energized when following trainsoccupy the respective approach sections on both or said tracks, prior toa preceding train having left the approach section for the opposingsignal on that particular track; a time element device; a manuallyoperable contactor, track sections be tween said opposing signals foreach track; cir-- cuit means for rendering said device operable when afirst route relay drops, providing said track sections are unoccupied;circuit means for dropping said first route relay upon operation of saidcontactor; circuit means for allowing a second route relay to beenergized only after said device has completed its operation, providingsaid device is rendered operable; and circuit means for clearing eachsignal only when its respective route relay is energized.

8. In a traffic control system for railroads; a track layout having aplurality of conflicting routes; signals for governing trafilc in bothdirections over each route; an approach section for each signal; adetector track section for each route; a route relay for each route;circuit means for energizing each route relay when an approach sectionto that route is occupied by an approaching train and for deenergizingsuch relay when the detector track section for that route becomesoccupied; circuit means for allowing the energization of only one routerelay at any one time; a single relay for each track for preventing theenergization of the route relay for that track when one or the other ofsaid approach sections for that track is occupied by a train after thetrain has left the detector track section for that route; and circuitmeans for clearing each signal when its respective route relay isenergized.

9. In an automatic crossing signalling system, the combination with arailway crossing including two railway tracks crossing each other, asignal for each track for governing the movement of railway vehiclesover said crossing, a route relay for each signal, circuits forenergizing said route relays so interlocked that only one of said routerelays may be energized at one time, an approach section for each signalincluding a track circuit and a track relay, a clearing circuit for eachsignal including a front contact of its associated route relay, andmeans effective if one of said signals is at proceed and both of saidtip proach sections are occupied for deenergizing the route relay forsaid one signal and putting said one signal to stop and causing theother route relay to be energized to clear its associated signalirrespective of the order in which said approach S ctions were occupied.

10. In an automatic crossing signalling system, the combination with arailway crossing including two railway tracks crossing each other, asignal for each track for governing the movement of railway vehiclesover said crossing, a route relay for each signal, circuits forenergizing said route relays so interlocked that only one of said routerelays may be energized at one time, an approach section for each signalincluding a track circuit and a track relay, a clearing circuit for eachsignal including a front contact of its associated route relay, andmanually operable means effective if operated when one of said signalsis indicating proceed and both of said approach sections are occupiedfor deenergizing the route relay for said one signal and putting saidone signal to stop and causing the other route relay to be energized toclear its associated signal irrespective of the order in which saidapproach sections were occupied.

11. In an automatic crossing signalling system, the combination with arailway crossing including two railway tracks crossing each other, asignal for each track for governing the movement of railway vehiclesover said crossing, a route relay for each signal, circuits forenergizing said route relays so interlocked that only one of said routerelays may be energized at one time, an approach section for each signalincluding a track circuit and a track relay, a clearing circuit for eachsignal including a front contact of its associated route relay, andmeans effective if one of said signals is at proceed and both of saidapproach sections are occupied for deenergizing the route relay for saidone signal and putting said one signal to stop and causing the otherroute relay to be energized to clear its associated signal after thelapse of a predetermined time irrespective of the order in which saidapproach sections were occupied.

12. In an automatic crossing signalling system, the combination with arailway crossing including two railway tracks crossing each other, asignal for each track for governing the movement of railway vehiclesover said crossing, a route relay for each signal, circuits forenergizing said route relays so interlocked that only one of said routerelays may be energized at one time, an approach section for each signalincluding a track circuit and a track relay, a clearing circuit for eachsignal including a front contact of its associated route relay, andmanually operable means effective if operated when one of said signalsis indicating proceed and both of said approach sections are occupiedfor deenergizing the route relay for said one signal and putting saidone signal to stop and causing the other route relay to be energized toclear its associated signal after the lapse of a predetermined timeinterval irre spective of the order in which said approach sections wereoccupied.

13. In an automatic crossing signalling system, the combination with arailway crossing including two railway tracks crossing each other, asignal for each track for governing the movement of railway vehiclesover said crossing, a route relay for each signal, an approach sectionfor each signal including a track circuit and a track relay, circuitsfor energizing said route relays including back contacts of theirassociated approach track relays and so interlocked that only one ofsaid route relays may be energized at one time, a clearing circuit foreach signal including a front contact of its associated route relay, andmeans efiective if one of said signals is at proceed and both of saidapproach sections are occupied for deenergizing the route relay for saidone signal and putting said one signal to stop and causing the otherroute relay to be energized to clear its associated signal irrespectiveof the order in which said approach sections were occupied.

JOHN I. VAUGHN.

